The present invention relates to a vehicle-onboard signal processing device, for example, a radar system, automobile navigation system, and the like, which is mounted on a vehicle in order to receive and transmit signals between the vehicle and the outside.
In a radio-wave type radar system that uses radio waves of millimeter wave band, the attenuation of radio beam is small even during the bad weather where rain or fog is present, so that the maximum detection distance required for a vehicle-onboard device can be ensured. For this reason, the radio-wave type radar system has been merchandised as a sensor for measuring the distance between the own car and a car ahead or measuring the relative velocity. Such a vehicle-onboard radar system is to be equipped with various magnetic shields to prevent electromagnetic noise from leaking to the outside and also from entering from the outside.
For example, in a device disclosed in Japanese application patent laid-open publication No. Hei 7-66746, a cylindrical shaft made of conductive material is disposed between the inside surface of an outer housing and an internal circuit, and signal lines and the like are placed inside the cylindrical shaft so as to increase the cut-off frequency in the space between the internal circuit and the inside surface of the outer housing and also to block electromagnetic noise generated from the signal lines, and the like.